Bats and Poop-Eating Pitcher Plants: a Perfect Partnership

Nature is full of unexpected pairings. Some are just interesting, like when long-billed birds clean the mouths of hippos. Others are clearly one sided, like in the case of jellyfish-surfing lobsters. However, the unusual attraction between pitcher plants and bats might just take the cake for most disgusting partnership in the natural world.

Pitcher plants are one of the most common types of carnivorous plants known to man, but are an absolute nightmare for insects. Unsuspecting bugs and even lizards get drawn into the plant's deep throat with the promise of sweet-smelling nectar at its base. But when the prey has had its fill and decides to leave, it quickly learns that the sides of the throat are too slippery to climb out. Eventually the prey succumbs to exhaustion, and is slowly digested by the horrific plant's juices. Some pitcher varieties can even turn their slippery coating on and off depending on the time of day, causing entire ant colonies to let their guard down around this seemingly 'intelligent' predator.

However, some pitcher plants don't need to go tricking ants to get a good meal. According to a study recently published in the journal Current Biology, one pitcher plant has developed a specialized 'reflector' that is acoustically attractive to bats* - an adaptation that can earn it a full meal of bat guano right down the throat. (Scroll to read on...)

"With these structures, the plants are able to acoustically stand out from their environments so that bats can easily find them," Michael Schöner of Ernst-Moritz-Arndt-University of Greifswald in Germany explained in a statement. "Moreover, the bats are clearly able to distinguish their plant partner from other plants that are similar in shape but lack the conspicuous reflector."

According to Schöner, this revelation solves a mystery that had been vexing carnivorous plant experts for years; compared to their deep-throated relatives, the plant species Nepenthes hemsleyana had always seemed far less efficient at capturing prey, and yet, remained healthy and prevalent in the natural world.

It was determined that for some reason, Hardwicke's woolly bats (Kerivoula hardwickii) often opted to roost in these plants, treating them almost like little 'bat cozies.' That led researchers to an idea: "Wouldn't it be neat if pitchers somehow advertised their presence to the bats?"

To find out, Schöner and his colleagues turned to Ralph Simon from the University of Erlangen-Nuremberg. Simon had been studying the acoustic adaptations of bat-pollinated flowers for some time, having determined long ago that some species boast dish-shaped petals or leaves to reflect high-intensity bat calls. (Scroll to read on...)

Using an artificial biomimetic bat head that emits and records ultrasounds, Simon tested the acoustics of the pitcher plant, finding that it's back wall was perfectly shaped to reflect bat signals. A series of tests even revealed that bats preferred roosting in plants whose reflector was in-tact, as opposed to one with reduced acoustic properties.

Of course, N. hemsleyana isn't looking for pollination. However, the researchers determined that by acting like the perfect bat latrine, the species was getting all the nutrients (namely nitrogen) it could ever want, enabling it to live in even the poorest kinds of soils.

"Carnivorous plants in general have already solved the problem of nutrient deficiency in a very unusual way by reversing the 'normal system' of animals feeding on plants," Schöner says. "It is even more astonishing that in the case of N. hemsleyana the system is taking a new turn."

He explained that while other pitcher plant species still have to digest their meals, this plant has bats do the job for them, and all they had to do is 'stomach' piles of bat guano. No one said ingenuity had to sound tasty!

*Want to support the conservation of these intriguing partners and other bats? Click here!

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